Network Working Group                                       M. Davison
Request for Comments: 2601                               Cisco Systems
Category: Standards Track                                    June 1999


                ILMI-Based Server Discovery for ATMARP

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

  This memo defines how ILMI-based Server Discovery, which provides a
  method for ATM-attached hosts and routers to dynamically determine
  the ATM addresses of servers, shall be used to locate ATMARP servers.

1. Introduction

  Presently, configuring a host or router to use ATMARP [1] is
  cumbersome and error-prone since it requires at least one ATM address
  to be statically configured on each host or router in the network.
  Further, it is impossible to implement a diskless host to use ATMARP
  since local configuration is required.  ILMI-based Server Discovery,
  hereafter referred to as "server discovery," provides a solution to
  these problems.

  A brief overview of the Integrated Local Management Interface (ILMI)
  and the Service Registry MIB, as defined by the ATM Forum, are
  provided in this memo. The reader should consult [2] for a complete
  description of ILMI and this MIB, but the information contained here
  is sufficient for an understanding of its use to support ATMARP
  server discovery.

2. Integrated Local Management Interface

  The Integrated Local Management Interface (ILMI) [2] provides a
  mechanism for ATM-attached devices, such as hosts, routers, and ATM
  switches, to transfer management information. It is based on the
  Simple Network Management Protocol (SNMP), Version 1, and supports



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  get, get-next, set and trap operations.

  The ILMI specification designates the switch side of the ATM link as
  the 'network side' and the host/router side of the ATM link as the '
  user side.' The Service Registry MIB, which is outlined in Section 3,
  is implmented on the network side and is queried from the user side.

3. ILMI 4.0 Service Registry MIB

  Server discovery utilizes the Service Registry MIB defined by the ATM
  Forum in ILMI Specification Version 4.0 [2]. To support the existing
  framework for IP over ATM, ATM switches must support the Service
  Registry MIB.

  A row in the service registry table [2] is defined as:

     AtmfSrvcRegEntry ::= SEQUENCE {
         atmfSrvcRegPort          INTEGER,
         atmfSrvcRegServiceID     OBJECT IDENTIFIER,
         atmfSrvcRegATMAddress    AtmAddress,
         atmfSrvcRegAddressIndex  INTEGER,
         atmfSrvcRegParm1         OCTET STRING
     }

  The definition of each field in this structure is:

     atmfSrvcRegPort - The ATM port number for which this entry
         contains management information. The value of zero may be used
         to indicate the ATM interface over which a management request
         was received.

     atmfSrvcRegServiceID - This is the service identifier that
         uniquely identifies the type of service at the address
         provided in the table. (See Section 3.2 for ATMARP OID.)

     atmfSrvcRegATMAddress - This is the full address of the service.
         The ATM client will use this address to establish a connection
         with the service.

     atmfSrvcRegAddressIndex - An arbitrary integer to differentiate
         multiple rows containing different ATM addresses for the same
         service on the same port.

     atmfSrvcRegParm1 - An octet string whose size and meaning is
         determined by the value of atmfSrvcRegServiceID.

  The service registry table is indexed by atmfSrvcRegPort,
  atmfSrvcRegServiceID and atmfSrvcRegAddressIndex.



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3.1 Service Parameter String

  A generic parameter string is defined in the service registry table,
  thus allowing protocol-specific parameters to be specified. To be
  consistent with [1], the parameter string for ATMARP shall be:

      ar$pro   16    bits     Protocol type
      ar$plen   8    bits     Length of protocol address
      ar$addr  plen  octets   Network address
      ar$mask  plen  octets   Network mask

  Where

     ar$pro  - see Assigned Numbers for protocol type number for
               protocol using ATMARP. (IPv4 is 0x0800, IPv6 is 0x86DD)

     ar$plen - Length of the protocol address. (IPv4 is 4, IPv6 is 16)

     ar$addr - Network address represented in network byte order

     ar$mask - Network mask represented in network byte order

3.2 Service Object Identifier

  This OID, assigned in the ATM Forum Service Registry MIB, names
  ATMARP within the context of server discovery.

   atmfSrvcRegATMARP  OBJECT IDENTIFIER ::= { 1.3.6.1.4.1.353.1.5.3 }

  It does not name any managed objects, rather is used to locate
  appropriate rows in the service registery table.

4. ATMARP Client Behavior

  An ATMARP client will access the service registry table via ILMI
  using the SNMP GetNext operator to "sweep" (SNMP parlance for a
  linear search) beginning with {Port = 0, ServiceID = <see Section
  3.2>, Index = 0} while holding the port number and the serviceID
  constant. (Port number 0 is used within ILMI to indicate "this
  port.")

  An ATMARP client with no local configuration, such as a diskless
  workstation, must use the row with the lowest index value if multiple
  ATMARP servers, possibly for multiple networks, are listed.

  ATMARP clients that have local IP configuration must use a row that
  has the appropriate IP address.  For example, consider the case where
  an IP router has 3 logical interfaces defined on a single physical



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  interface with IP addresses 1.0.0.1/8, 128.10.0.1/16 and
  171.69.150.226/24. The router will sweep the service registry table
  looking for rows that have atmfSrvcRegParm1 values as shown below:

      Network number/mask  atmfSrvcRegParm1
      -------------------- --------------------------------------
      1.0.0.0/8            08 00   04   01 00 00 00   ff 00 00 00
      128.10.0.0/16        08 00   04   80 0a 00 00   ff ff 00 00
      171.69.150.0/24      08 00   04   ab 45 96 00   ff ff ff 00

  When the correct atmfSrvcRegParm1 values are located, the router may
  then establish an SVC to the selected server and perform the
  appropriate protocol operations.

  Redundant ATMARP servers are supported with multiple rows in the
  service registry table. This list of ATMARP servers is ordered with
  the primary ATMARP server having the lowest index value. The ATMARP
  client must attempt to utilize the primary ATMARP server before
  utilizing a secondary ATMARP server. Administrators must ensure that
  the listed ATMARP servers are synchronized.

5. ATMARP Server Behavior

  An ATMARP server shall be locally configured. The ATMARP server may
  retrieve the ATMARP service registry data to validate the results. If
  an incorrect row is retrieved the error may be flagged in a locally
  significant way.

6. Relationship with PNNI Augmented Routing

  An augmented version PNNI ("PNNI Augmented Routing," or PAR) [3] has
  been developed by the ATM Forum. PAR can distribute data such as
  ATMARP server addresses. Further, the ATM Forum is developing a proxy
  mechanism for PAR (Proxy PAR) that would allow a UNI-attached host or
  router to access PAR data without a full PAR implementation.  These
  mechanisms offer a promising way to manage the service registry
  tables maintained on each switch in an ATM network, yet would not
  require changes to the mechanism defined in this memo. Hosts and
  routers can continue to utilize ILMI-based or Proxy PAR-based server
  discovery and network administrators could manage the service
  registry data with local configuration or via PAR and Proxy PAR.










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7. Security Considerations

  The server discovery mechanism is built on the ILMI managment
  framework and the security embodied in that framework. Access, to
  user- or network-side information is controlled by MIB design rather
  than protocol security mechanisms.

  The service registery MIB, the table containing information for
  server discovery, is defined in [2] with read-only access. This means
  that any user-side device may query the service registry, but may not
  modify the service registry via ILMI. Instead, the sevice registry
  table must be modified via local configuration on the ATM switch.

References

  [1]  Laubach, M. and J. Halpern, "Classical IP and ARP over ATM," RFC
       2225, April 1998.

  [2]  ATM Forum, "Integrated Local Management Interface (ILMI)
       Specification Version 4.0," af-ilmi-0065.000, September 1996.

  [3]  ATM Forum, "PNNI Augmented Routing (PAR) Version 1.0," af-ra-
       0104, January 1999.

Author's  Address

  Mike Davison
  Cisco Systems
  170 West Tasman Drive
  San Jose, California 95134

  Phone: (408) 526-4000
  EMail: [email protected]


















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Full Copyright Statement

  Copyright (C) The Internet Society (1999).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published
  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph are
  included on all such copies and derivative works.  However, this
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
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  followed, or as required to translate it into languages other than
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  The limited permissions granted above are perpetual and will not be
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  This document and the information contained herein is provided on an
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.



















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